Semiconductor memory device and manufacturing method thereof

Abstract

A semiconductor memory device includes: a silicon substrate having a main surface; n + diffusion layers formed on the main surface of the silicon substrate distanced from each other; HDP oxide films formed on the n + diffusion layers and deposited on the main surface so as to protrude above the main surface; an ONO film (a stacked film of an oxide film, a nitride film, and an oxide film) as a charge holding layer formed between the HDP oxide films; and a gate electrode (a polysilicon film and a doped polysilicon film) extending over the ONO film and the HDP oxide films.

1. A semiconductor memory device, comprising:
 a semiconductor substrate having a main surface; 
 first and second impurity regions formed on said main surface of said semiconductor substrate distanced from each other; 
 first and second insulating films formed on said first and second impurity regions, respectively, and deposited on said main surface so as to protrude above said main surface; 
 an ONO (Oxide-Nitride-Oxide) film formed between said first and second insulating films; 
 a gate electrode extending over said ONO film and said first and second insulating films; and 
 a sidewall insulating film formed on a sidewall of said first and second insulating films and reaching said impurity region. 
 
     
     
       2. The semiconductor memory device according to  claim 1 , wherein
 upper surfaces of said first and second insulating films are positioned higher than an upper surface of said ONO film, 
 said gate electrode has a downwardly-protruding portion on said ONO film, 
 said sidewall insulating film is further formed on a sidewall of said downwardly-protruding portion, and 
 a suicide film is formed at a surface of said first and second impurity regions that is not covered by said sidewall insulating film.